1. Technical Field
This invention relates generally to procedures and equipment for hot tapping a pipeline, and more particularly to a hot tapping method and valve that provide increased component flexibility as well as size, weight, and cost advantages.
2. Description of Related Art
"Hot tapping" refers to the procedures and equipment a worker employs to add a branch connection to an existing pipeline while it contains a fluid (often pressurized) without shutting down service. Any size and type of pipeline may be involved. To hot tap a line, the worker bolts or welds a fitting on a section of pipe in the line to form a tapping outlet structure (e.g., a flange). Next, he takes a conventional gate valve or other suitable hot tapping valve and bolts the upstream side of the valve body on the tapping outlet.
Once the tapping valve is mounted on the pipe, he bolts a conventional hot tapping machine to the downstream side of the valve body. The hot tapping machine includes a motorized hole saw for sawing a hole in the pipe. After mounting it and pressure testing the hookup, the worker advances the hole saw through the body of the tapping valve with the valve mechanism in an open position. Next, he saws a hole in the wall of the pipe.
He then proceeds by retracting the hole saw sufficiently to close the valve mechanism of the tapping valve. After closing the tapping valve, he removes the tapping machine. That leaves the closed tapping valve connected to the pipeline and ready for service, and he may then connect a pipe, gauge, sensor, or other component to the downstream side of the valve body and open the valve when desired.
Hot tapping a line that way is well known. However, the size, weight, and expense of the gate valve employed can present problems, especially for 24 inch to 48 inch and larger pipelines. Although butterfly valves are usually smaller, lighter, and less expensive than gate valves, the conventional hot tapping procedures just described do not work with them. Existing hot tapping procedures do not work with many other components either, including globe valves, check valves, back flow preventers, and no-valve technologies. Therefore, workers need a better way for hot tapping an existing pipeline.